The purpose of this protocol is to determine if a diet emphasizing consumption of low glycemic carbohydrates facilitates maternal post-partum weight and fat loss. Twenty pregnant women will be recruited from our on-going exercise in pregnancy study and randomized into one of two diet groups, low glycemic and high glycemic. Subjects will start the appropriate diet at 36 weeks gestation and continue until four months postpartum. Subjects will eat a diet containing 15-20% of their calories from protein, 55-60% of the calories as carbohydrates, and <30% of the calories from fat. Diet compliance will be assessed by collecting at least one 24-hour recall per week. Weight will be monitored weekly; skinfolds will be monitored monthly in the post-partum period.